Rudimentary power line carrier-current communication (PLCC) systems have been in use for many years. By way of example, in the early 50's PLCC units were commercially available that plugged into household power lines. These units enabled a parent to monitor an infant crying in a remote bedroom via power line carrier (PLC) transmitting and receiving units. Similarly, PLC based units permitted music generated in one location in a house to be transmitted to other points in the house via the power lines. PLC technology has also been used to implement and control various household functions. For example, a central PLC control station has been used to remotely control household lights and home appliances.
However, due to lack of reliability, PLCC systems have typically not been utilized in applications where loss of life could result if the system failed to consistently perform properly. Contrasted to the present invention, prior art PLC based systems have significant disadvantages. For example, prior art PLC control systems are extremely slow (e.g., conventionally about 50 bits per second) and do not permit bidirectional transfer of information. Additionally, because of a lack of satisfactory high voltage protection circuitry, prior art systems are susceptible to disruption caused by high voltage surges on the power lines such as often are produced, for example, by lighting strikes. Also, prior art PLC systems are typically amplitude modulated, and have very high error rates due to various sources of ambient power line noise.
One prior art example of a PLC communication network, U.S. Pat. No. 5,034,882 to Eisenhard et al issued Jul. 23, 1991, is known to employ distributed intelligence among a plurality of preprogrammed cells. However, the Eisenhard system contemplates using a conventional prior art transceiver for digital data and, moreover, does not perform any processing on the transmitted data. As such, the Eisenhard system still retains the poor data reliability and inadequate noise immunity inherent in prior art PLCC systems. Another prior art example using PLC communication is provided in U.S. Pat. No. 4,234,926 to Wallace et al, issued Nov. 18, 1980. The Wallace system utilizes remote data acquisition units which monitor conditions of transportable containers and sends data regarding those conditions over existing on-site power wiring to a central monitoring computer. However, the Wallace system does not envision a distributed intelligence system enabling monitoring and control of equipment at remote sites and, moreover, provides only a single, separate signal transfer unit located in proximity to the central monitoring computer to assist in reducing noise-induced operating problems.
The following list of prior issued patents (which is by no means exhaustive) describe various aspects of power line communication systems:
______________________________________ Pat. No. Issued Inventor(s) ______________________________________ 4,311,964 Jan. 19, 1982 Boykin 4,328,590 May 4, 1982 Lee 4,885,564 Dec. 5, 1989 Vercellotti et al 4,885,563 Dec. 5, 1989 Johnson et al 4,815,106 Mar. 21, 1989 Propp et al 4,715,045 Dec. 22, 1987 Lewis et al 4,675,648 Jun. 23, 1987 Roth et al. 4,644,547 Feb. 17, 1987 Vercellotti et al 4,580,276 Apr. 1, 1986 Andruzzi, Jr. 4,567,557 Jan. 28, 1986 Burns ______________________________________
In accordance with a preferred embodiment of the present invention, the LAN consists of numerous communications nodes positioned at physically separate locations. Each node in the LAN consists of an intelligent Terminal Unit or a Data & Control Unit that utilizes the local AC power lines as the common bus over which it bidirectionally communicates with other communications units at other nodes. By using PLC communication techniques, there is no need to run dedicated cabling between LAN nodes. Moreover, PLC communication is more "survivable" during a conflagration or other destruction than dedicated cabling or fiber optic communication systems.
The PLC local area network distributed intelligence communications system disclosed herein, overcomes many of the disadvantages of the prior art identified above. In accordance with a preferred exemplary embodiment of the present invention, each Terminal Unit of the PLCC LAN is provided with an intelligent controller (hereinafter referred to as a "distributed artificial intelligence embedded controller" or DAIEC) that communicates with any other Terminal Unit or node in the network and provides an interactive operator interface through a touch-screen CRT display device. Moreover, the DAIEC in each Terminal unit includes a local non-volatile random access memory and maintains a data base of ship casualty and damage control information (referred to herein as the ship engineering casualty and damage control data matrix or SECDCDM). In addition, each communication node in the LAN utilizes an improved carrier-current transmitter and receiver circuitry that significantly increases the overall speed, noise immunity and reliability of PLC communications on the LAN. (For example, transmission rates greater than 55 Kbytes/sec and undetected error rates of less than 10.sup.-11).
An exemplary embodiment of the present invention is described herein as an "engineering casualty and damage control" management system and is intended for installation and use within, for example, a U.S. Navy ship or Coast Guard cutter. In general, engineering casualty control is concerned with the prevention, minimization and correction of the effects of operational and battle damage to the machinery, electrical systems and piping installations. Whereas, "Damage control" is concerned with such things as the preservation of stability and watertight integrity, the control of fires, and the control of nuclear, biological, and chemical contamination. An example of "battle damage" is the physical damage resulting from a bomb or a missile hitting the ship. Some examples of "operational damage" are damages resulting from fire, collision, grounding (i.e., running aground), weather or equipment explosion.
In a catastrophe, it is critical that an automated system operate reliably and quickly. For example, lives can be saved by quickly preventing occupied areas of the ship from filling with smoke or water. Further damage can be averted by knowing and managing the fire or flooding so that the ship may continue fighting. In addition, the archiving of shipboard data for later study and training can be of great importance in improving the management of future catastrophes.
The PLCC arrangement in accordance with the present invention provides a particularly advantageous technique for implementing a shipboard damage control management system. Power cables in all US fighting ships have fused main and alternate feeds. Additionally, if one line of a three phase power line shorts to the deck, the power and signals on the power line will not be lost. (As an example, after the massive combat fires in the USS STARK and HMS SHEFFIELD, each ship's power distribution system was still functional.) Additionally, such shipboard power cables are extremely large and strong. Thus, even in the midst of an anti-ship missile-caused fire, a ship power line cable is far more likely to remain intact than other cable. Fiber optic cables are extremely fragile when compared to power cables. Fiber optic cables are not readily repairable at sea whereas ship's company has experience in the quick repairing of power cables.
More of USS STARK's company died due to smoke inhalation than died as a direct result of the two missile hits. These people were trapped in a smoke infested area of the ship. They had no means to communicate with other parts of the ship, and no one knew where they were. If a PLC LAN terminal unit in accordance with the present invention had been available, they could have communicated over the power lines and been saved. In accordance with a preferred exemplary embodiment of the present invention, a data matrix stored at each terminal unit will contain updated data from sensors located throughout the ship and provide a means to identify any trapped members of a ship's company.
The initial shock of the missile hits in USS STARK caused a disruption of the ship's primary electrical power. The result was that STARK was unable to either defend herself or conduct effective damage control. There were two causes for the loss of power. First, shock sensitive circuit breakers opened on missile impact. Second the impacting missile broke a primary power line. Lack of information about the open breakers and the broken power line prevented the establishment of a power system reconfiguration plan. Since the shipboard breakers and switches were not able to be controlled remotely, primary power was never reestablished. Without electrical power in an all electric ship, effective efforts to fight the fire were not possible. Analysis conducted after the fire showed that with the proper information concerning the power distribution system, the power could have been restored.
Review of data from ship fires shows that smoke will propagate through a ship in about 4 minutes. The preferred embodiment of the present invention provides a method and means for obtaining the establishment of smoke-tight, fire-tight boundaries within 24 seconds from the start of the fire. (This is only 10 percent of the time it would take for a ship to be completely filled with smoke). As such, complete restoration of electric power must be accomplished in less than 5 seconds to assure that smoke-tight, fire-tight boundaries can be set within 24 seconds.
Another damage control asset to be considered is fire fighting water. In a fire on the USS STARK, the destruction of the main fire fighting water line rendered the ship unable to develop adequate fire main pressure. (A nearby tug prevented the loss of the USS STARK). In accordance with the preferred embodiment of the present invention, after accumulating and storing data from sensors throughout the fire fighting water subsystem, the fire water main layout can be manually or automatically reconfigured to accommodate the reduced capacity caused by a broken fire fighting water main.
Moreover, there are various pieces of ship equipment that must be available when a conflagration is imminent or when the ship is performing a particular operation. Conventionally, most major pieces of ship's equipment have safeguards built into them which prevent damage caused by overload. One example is the gas turbine that drives the electrical generators for the ship. Sensors and controls are provided to prevent turbine overload. If, for example, the turbine was operated for longer than ten seconds at an output capacity that is greater than 105 percent of its rated capacity, it would ordinarily be automatically shut down. Operation at 105% of capacity would not destroy the turbine. It would, however, reduce the life of the turbine perhaps 100 hours per hour that the turbine operates at 105%. As load increases above 105% the reduction in life of the turbine will be accelerated. At 115 percent of rated load the turbine may have its life reduced by 500 hours for each overload hour.
On a military vessel, a missile system is required for effective offensive actions and for the defense of the ship. Conventionally, as a part of the missile guidance system, the ship provides a microwave signal to the missile while in flight. This microwave energy is called the "Rear Reference" signal. Safety considerations require that the missile must be able to destroy itself if it malfunctions. This safety consideration is known as "Self Destruct". The procedure for Self Destruct is that whenever the Rear Reference signal is absent or removed, the missile warhead automatically detonates.
The following exemplary scenario illustrates the interrelationship between a few of the diverse ship systems that the inventors have recognized must be organized and controlled during a typical conflagration: assume the notional ship discussed above is operating on only one turbine of its three turbines and that particular turbine is running at 98 percent of capacity. The ship comes under attack by two inbound exocet missiles and has launched four missiles in its defense. The main mess compressor or some piece of ancillary equipment subsequently turns on. The compressor current causes the sole gas turbine to go to 105 percent of capacity. The turbine overload control shuts down the turbine. The ship is now without power. The rear reference signal stops because of loss of power to the microwave transmitter. Loss of the rear reference signal from the ship causes the missiles to self destruct. The powerless ship is now also defenseless. The exocet missiles hit the ship for two reasons: first, the ship had no coordinated way to remove overload protection from the turbine; second, the ship had no coordinated way to remove non-essential loads.
This type of removal of protection is called "battle shorting". For example, opening a radar transmitter's cabinet door will shut down the transmitter due to sensing switches in the doors. Battle shorting removes these safeguards. The designer of the transmitter understood that the safety of the entire ship must come before the safety of the person opening the door. Currently, however, there is no central control or monitoring of these features in a conventional Navy ship. Moreover, in the engineering plant of a conventional US Navy ship there is currently no battle shorting of major pieces of equipment. In a situation where the battle shorting of a major piece of equipment such as the ship turbine becomes necessary, there are certain procedures that should be followed. For example, if the turbine is going to be battle shorted, the percentage of overload should be monitored by someone of appropriate authority in the engineering chain of command. (Ultimately, it may be the responsibility of the commanding officer of the ship to decide if he should risk destroying the turbine rather than shutting it down). Moreover, the shutting off of other nonessential loads (e.g., the mess compressor) would also reduce the likelihood of a turbine overload. This technique is called "load shedding". Decisions regarding the timely load shedding of various pieces of equipment should also be made by one having the appropriate authority. Accordingly, a preferred exemplary embodiment of the present invention makes battle shorting and load shedding of major pieces of ship equipment feasible by providing centralized monitoring and control facilities at strategic locations throughout the ship.
In accordance with an exemplary preferred embodiment of the present invention, a list of non-essential equipments is arranged in a data base (i.e., the SECDCDM) stored in non-volatile memory in each Terminal Unit and is utilized to indicate equipment that can be removed from service. Likewise, a list of essential equipments that must remain in service, almost without regard for equipment life and ships company safety, is also stored in the data base at each terminal. One engaged in the art of military ship design would appreciate that these two lists will differ as the operational modes of the ship are changed. For example, during a storm, ship's command should be able to shut down the radar and battle short the anchor windlass rather than run aground.
The combination of the high reliability of PLC communication using the improved transceiver of the present invention along with the equipment monitoring, integrated battle shorting, load shedding and distributed intelligence data management methods disclosed herein in accordance with the preferred exemplary embodiment of the present invention, will significantly enhance the survivability of modern warships and commercial vessels.